The reservoir dam at Bukit Gombak.

   On the evening of 15 July 2021, newsfeed and videos started trending on social media about a strange incident at Bukit Batok West Ave 5 beside the Gombak Stadium.
Muddy water was gushing out at a tremendous rate from a hillside near the Bukit Gombak MRT Station.

Videos above copyright and courtesy of Marcus Lim

One of these posts was from my friend, historian painter Mr Marcus Lim, who was an eyewitness to the event. In his post, he also pondered over what was happening. It was an incredible scene.

Oh Gosh! The Seng Chew Dam burst? I speculated.
Dam? Came the more incredulous response from Marcus.

In reality, what had happened was that a part of the Seng Chew lakeside wall had collapsed inwards after a few days of rain previously and slid into the lake. The landslide caused a mini-tsunami to overflow the top and gush down the hill towards the roadside at West Ave 5. The resulting deluge flooded the roadside, stopping traffic for several hours and bringing with it debris like tree branches, logs and lots of mud.

THE SENG CHEW QUARRY LAKE
Some of you may not be aware but there is a hidden lake high up on Bukit Gombak.

The Seng Chew Quarry Lake at Bukit Gombak

It was formed from the disused granite quarry that operated there from 1947 till 1970.
It was called the Seng Chew Granite Quarry.

This disused quarry was transformed and revitalised into a lake as part of the new Bukit Gombak Nature Park and Forest Trail. It was to be one of the several features of the new Bukit Batok Town Park that included the new sports stadium and the Little Guilin Park.
(Note: The Bukit Batok Nature Park is a different park about 2km away)

However, the Bukit Gombak Nature Park and the Seng Chew Quarry Lake were short-lived, and were soon closed to the public due to several recurring landslides that occured in that area. These occurred at several places like Chu Lin Park, the Forest Trail and at the lake side as well. The public thus were denied entry for safety reasons. Only the Little Guilin Park remained open to the public.

You can read some my earlier articles about the Bukit Batok Town Park and the Seng Chew Quarry at the links here, here, here or here et al.

This was a landslide into the lake back in 2014.

The lake boundary was fenced up for public safety.

Bukit Gombak Nature Park was closed due to recurring landslides.

This was the latest landslide of 15 July 2021 that caused the lake to overflow.

The debris and mudslide from the overflowing lake spilled onto the roadside below.

That may well have been the end of the story, but why did I exclaim that the Dam burst to Marcus' amusement?
Well, while some of you may know of the existence of this hidden lake, most of you will never ever know that there is a huge dam there at Bukit Gombak! Surprised?

It was so well engineered and built that you would never ever suspect that it is there.
Marcus would have been thinking I might be crazy when I said the dam burst, as would most of you. You have in your mind a dam such as the one like China's Three Gorges or Hoover Dam in USA.
A great hulking concrete structure holding back gadzillion tons of water and with a hydroelectric power station inside. Am I right? Touch your heart, ha ha.

THE SENG CHEW QUARRY DAM

The Seng Chew Quarry Dam is technically known as an earth-filled 'Embankment Dam'.

When the HDB was building Bukit Gombak New Town in the early 80s, they had a gigantic problem that they needed to settle. This was the scarred western hillside of Bukit Gombak where there were four huge former granite quarries. These were the Ideal Home Quarry, the Lian Hup Quarry, the Seng Chew Quarry and the Gammon Quarry. 
*(There was a fifth smaller quarry between Gammon and Seng Chew, but that will be fodder for a new article in future)

These quarries had gouged enormous holes into the landscape.  HDB architects decided to convert the quarries into nature parks as they were unsuitable for other major infrastructure then.  Both the Gammon and Seng Chew Quarries had to undergo major civil engineering works.

The aerial photo below shows the Seng Chew Quarry in 1956, in its ninth year of operations. There was another smaller adjoining quarry to its right by 1970 when it was closed but I cannot find a photo of that era. So you can imagine how much more wider the quarry face would have been after a further 14 years of quarrying.

This is the same 1956 quarry photo superimposed on a current Google map extract. The circle approximates the quarry-face size in 1970 according to topographic maps of the 70s. That was how much larger the quarry had grown before mining operations ceased. For reference, Bukit Gombak MRT Station is at bottom right.

Click on photo to see in full details.

The red circle represents the size of Seng Chew Quarry Lake today as it was planned by HDB to be part of the new Nature Park. 
In order to reduce it to that manageable size, they had to reinstate the entire hillside by building an earth dam over the entire area where the quarry once was. And so the 1st stage to constructing the lake was to build the new earth dam. Click on the photo above to see an enlarged view where you are able to judge the size of the 'hole' that they had to fill to build the earth dam.

The entire hillside between the Gombak Stadium and the Goodview Gardens HDB precinct

(left of pic) is in reality an earth dam that was built to enclose the Seng Chew Quarry Lake.

The hillslope behind the HDB's Goodview Gardens housing blocks are actually part of the earth dam.

This is the top of the earth dam that holds back the Seng Chew Quarry Lake reservoir. This was the zone where the landslide cause the lake waters to overflow and spill over the dam.
The drain on the right is known as a Spillway, it acts as a vent whenever the lake waters reaches a certain level and keeps the water level inside under control.
The sudden landslide on 15 July 2021 overwhelmed the capacity of the spillway and so the water simply overflowed this top but continued to follow the direction of the spillway.

The spillway drain after the deluge of 15 July.
Appears that some repairs will be needed soon.

So, in all essence, the spillway actually did its job well except that it wasn't designed for the kind of sudden volume that overwhelmed it that day.

My first instinct when I saw the video clips was that this area at the spillway top of the earth dam had collapsed and the earth dam had burst open. 

I reckoned that the earth dam is at least 300 metres wide and 30 metres high, holding back the reservoir that became the Seng Chew Lake. An amazing engineering feat. It had been so well incorporated into the landscape that almost everyone would never believe that it is a real dam.

So now you know that there is a huge earth dam at Bukit Batok.

Trekking Bukit Gombak in search of WW2 relics.

Last November, I wrote about the suspected World War 2 Japanese pillbox that may still exist on the slopes of Bukit Gombak. With the recent dry spell, it was perfect weather to organise a search and to identify the concrete structure, or what's left of it,

This morning a team of enthusiasts brought together over Facebook made the exploratory trip.
Among those who came along were Andrew and Christopher, who had previously been to the structure itself, Kim Frost, a WW2 vehicle expert and Jingyi, one of the few trained archeologist in Singapore, heritage blogger Jerome, and with experts from the Bukit Brown team, Andrew and Fabian.

I had brought together this team on my own premise that the structure there could possibly be Japanese or at least WW2 related. But, in order that I would not disappoint anyone if it turned out to be a wild goose chase, I decided to embellish the trip with some side itinerary.

1. A good mornings' hike up the hill.
2. An understanding of the geology of Bukit Gombak and the region.
3. A visit to the mysterious hidden lake at Bukit Gombak.
4. A history of the war in relation to Bukit Gombak.
5. The primary purpose - to view and identify the damaged concrete structure.

The trekkers reaching the base of the spur where the concrete structure is located.

Climbing the steep cliff face. Part of the concrete can be seen above/

Andrew cutting the vines to create a passageway.

The hidden lake near the top of Bukit Gombak.

Part of the concrete structure. Anyone recognise what these are?

Kim Frost digging and trying to identify the structure.

A large metal protrusion.

Were we able to positively identify the structure? Unfortunately, no.
There was simply not enough visual evidence to indicate what it was or what it was used for.  The structure was in total ruins as though it was purposely destroyed but this is not likely to be as Andrew and Christopher had seen the structure semi-intact before the roof caved in.

Even then, the group found other distractions at the site.
Apparently, some unknown people, probably the residents living in the nearby HDB flats, have created a sort of vegetable garden and it was thriving in this isolated hillside. Pandan, tapioca, pineapple, bananas, sugar cane and chillies were found in neat plots.
And, best of all, we discovered a new and easier route to the structure that didn't involve climbing the cliff!

A real Pandan garden

Alas, we also saw signs of a recent field survey, which could possibly mean that some sort of development might be on the cards for this place.

As for the concrete structure, I guess it has to be left to more professional people in future (if there is a future for it).

Here's a little trivia about Bukit Gombak which I shared with this group.
Bukit Gombak contains the oldest known rocks in Singapore.
Contrary to the misconception, Bukit Gombak is actually not made of granite but of another type of hard rock called Norite. Though one is easily forgiven for not knowing the difference.
Samples of norite can be seen strewn all over the Gombak hill.
Bukit Gombak Norite is estimated to be 500 million years old, in comparison to the granite of neighbouring Bukit Timah which is a young 250 million years old.

A geological map of Singapore,

Bukit Gombak as seen from the East (Upper Bukit Timah side)

Watch a clip of the Gombak Trek

The mysterious hidden lake of Bukit Gombak

Following my earlier posting of a video clip of the stream flowing from Bukit Gombak, my friend SK Yum sent me some pictures he took while exploring Bukit Gombak with his children a year ago.

He was surprised to find a lake at the top of the hill. The lake is the source where the stream flows endlessly till this day.

Here are the pictures he took of the stream and lake.
Read on further to learn some surprising facts about this lake.

My sincere thanks to Yum Shoen Keng for providing the personal photos above.

Though the lake has been there for as long as most Bukit Gombak town residents have lived there, the lake was only formed in the late 1970s.
This was when the government closed all the granite quarries in Singapore, (except for Gali Batu) and restricted quarrying offshore to Pulau Ubin.

The lake was formed when water started to fill the pit that was the old SENG CHEW Granite Quarry at Jalan Perang. It continues to fill till this day.

The stream that flows out from this lake acts as an overflow vent to drain excess water should the lake fill to the brim, which happens during intense rainfall. Otherwise, the lake is constantly fed by the natural Gombak springs.

Though not officially restricted as an out-of-bounds area, the lake is cordoned off due to the danger of sudden drop offs. NParks does not encourage visitors there as it is undeveloped with hidden dangers.

The old Jalan Perang Taoist Temple.
In the olden days, there used to be several shrines and one major Taoist temple along Jalan Perang.
The Jalan Perang Taoist temple was noted by residents near and far for its effective talismans given out at this temple.  This Taoist temple also had waters springing from Bukit Gombak which were eagerly collected by worshippers for its 'magical' or spiritual qualities. This temple and all the minor shrines at Jalan Perang were demolished during the construction of Bukit Gombak New Town.

Sorry I am not able to elaborate more on the Taoist temple
(I am not taoist and depended on hearsay for info on it).




Related links:
The old Gombak Nature Trail photos
Streams at Bukit Gombak
Bukit Gombak Nature Trail article